1. Field of the Invention
The present invention relates to a pumping system for gates, and more particularly to a pumping system for gates wherein a plurality of pumps are mounted to the liftable shifting sluice body.
2. Description of the Prior Art
In the conventional drainage canal, as shown in FIG. 8 of the attached drawings the natural drainage canal 28 is partitioned by a gate or sluice 25 at the downstream side and a switching gate or sluice 27 at the upstream side, and a pumping equipment 29 is installed near the drainage canal 28 upstream of the switching gate 27 in parallel therewith. Both gates 25 and 27 are usually open so as to carry out a natural drainage through the drainage canal 28 from the upstream side to the downstream side. However, when the water level in the downstream side becomes higher than that in the upstream side so that the natural drainage is impeded, the switching gate 27 is closed to prevent a countercurrent from occurring, and the pumps in the pumping equipment 29 are operated so that a forced drainage is carried out.
For this installation, an exclusive site having a broad area, a large foundation work for the civil engineering work and large buildings are required. In order to avoid these disadvantages a gate has already been proposed wherein a plurality of pumps are mounted to the liftable sluice body of a sluice in parallel with each other, and a forced drainage takes place by pumping the water in the upstream side to the downstream side, while a natural drainage takes place by raising the sluice body to open the water channel. See Patent Publication No.5883/1971.
However, in practicing this gate, at the time of the forced drainage, as the diameter of the pump becomes large, the necessary sank depth for the sluice body becomes large. Therefore, the weight of the sluice body becomes large and the net pump head of the pumps becomes large. Further, this causes the power for the pumps to increase, making the power of the motors and the initial power receiving capacity to be large. Moreover, when the necessary sank depth of the sluice body becomes large, since it becomes difficult to lower the water level of the upstream side, the difference in water level between the upstream and downstream sides or the pump head is decreased, causing a problem in that a sufficient drainage is not carried out. Another problem resides in that when the sluice body is raised at the time of the natural drainage the screens mounted at the upstream side are left as they are so that a smooth water flow is impeded.